ML093370762
| ML093370762 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/30/2009 |
| From: | - No Known Affiliation |
| To: | Division of License Renewal |
| References | |
| Download: ML093370762 (45) | |
Text
1 PrairieIslandNPEm Resource From:
Eckholt, Gene F. [Gene.Eckholt@xenuclear.com]
Sent:
Monday, November 30, 2009 2:00 PM To:
Plasse, Richard
Subject:
ACRS Slides Attachments:
December 3 PINGP ACRS Full Committee Presentation - NRC.pdf Rick Here is a pdf of our final ACRS presentation slides.
Gene Eckholt Project Manager License Renewal Project Prairie Island Nuclear Generating Plant Phone: 651-388-1121 ext. 4137
Hearing Identifier:
Prairie_Island_NonPublic Email Number:
1108 Mail Envelope Properties (71AC1869DEB82E47AAC75C450F60546A0BEAD6A39C)
Subject:
ACRS Slides Sent Date:
11/30/2009 2:00:16 PM Received Date:
11/30/2009 2:00:26 PM From:
Eckholt, Gene F.
Created By:
Gene.Eckholt@xenuclear.com Recipients:
"Plasse, Richard" <Richard.Plasse@nrc.gov>
Tracking Status: None Post Office:
enex04 Files Size Date & Time MESSAGE 199 11/30/2009 2:00:26 PM December 3 PINGP ACRS Full Committee Presentation - NRC.pdf 1187708 Options Priority:
Standard Return Notification:
No Reply Requested:
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Recipients Received:
1 Prairie Island Nuclear Generating Plant ACRS License Renewal Meeting December 3, 2009
2
Introductions
z Mark Schimmel - Site Vice President z Gene Eckholt - License Renewal Project Manager z Steve Skoyen - Engineering Programs Manager z License Renewal Project Team and Subject Matter Experts
3 Agenda z Site Description z ACRS LR Subcommittee Follow-Up Items z Questions
4 Site Description z Plant Owner, License Holder and Operator z Northern States Power Company - Minnesota z Subsidiary of Xcel Energy z Location z SE of Minneapolis-Saint Paul, MN z On Mississippi River
5 Site Description z Construction Permits Issued - June 1968 z Operating Licenses z Unit 1 z Issued August 1973 z Expires August 2013 z Unit 2 z Issued October 1974 z Expires October 2014 z LRA Submitted - April 2008
6 Site Description z Two 2 - Loop PWR Units z 1650 MWt z 575 MWe (Gross) per Unit z Westinghouse - NSSS z Pioneer Service & Engineering -
Architect/Engineer z Once-Through Cooling Supplemented with Four Forced Draft Cooling Towers (Seasonal) z Ultimate Heat Sink is Mississippi River via Cooling Water System
7 Site Description z Dual Containment Design z Steel Containment Vessel Within Limited Leakage Concrete Shield Building (5 Foot Annulus) z Steel Containment Vessel z Provides Primary Containment z Lower Head Encased in Concrete z 1-1/2 inch Thick Bottom Head, 1-1/2 inch Thick Shell, 3/4 inch Thick Top Head z 3-1/2 inch Thick at ECCS Sump Penetrations Containment Elevation
8 ACRS LR Subcommittee Follow-Up Items z Refueling Cavity Leakage z Condensate Storage Tank Examinations z Underground Medium Voltage Cables z Manhole Inspection Interval z Impact of Freeze/Thaw Conditions
9 Refueling Cavity Leakage Leakage History z Intermittent Refueling Cavity Leakage in Both Units Since Late 1980s z Estimated Leak Rate of 1-2 Gallons per Hour z Observed in ECCS Sump and Regenerative Heat Exchanger Room z Sealing Methods Used to Mitigate Leakage Were not Consistently Effective z Root Cause Performed in Early 2009 to Identify Permanent Solution
Refueling Cavity Leakage Path Leakage Observed in ECCS Sump and in Regenerative HX Room (below cavity)
Containment Elevation
11 Refueling Cavity Leakage Root Cause Evaluation z Root Cause Evaluation Completed in April 2009 z Sources of Leakage were Determined to be Floor Embedment Plates for Reactor Vessel Internals Stands and Rod Control Cluster Assembly (RCCA) Change Fixture z Exposure of Containment Vessel and Structures to Refueling Cavity Water Has Not Had an Adverse Impact on Their Ability to Meet Design Requirements
12 Refueling Cavity Leakage Root Cause Evaluation Typical Reactor Vessel Internals Stand Support Typical RCCA Change Fixture Support
13 Refueling Cavity Leakage Root Cause Evaluation Original Embedment Plate Configuration Existing 1/4" thk stainless steel cavity liner Existing seal weld to embedment plate not accessible. Failure of weld would result in leak Side View Existing cavity liner fillet weld to embedment plate Potential leak path along threads or under baseplate
14 Refueling Cavity Leakage Fall 2009 Unit 1 Repairs z Reactor Vessel Internals Stands and RCCA Change Fixture Embedment Plates Repaired z Existing Nuts Removed z Replaced with Blind Nuts z Blind Nuts Seal Welded to Baseplate z Seal Weld Applied Between Baseplate and Embedment Plate z Welds Examined by NDE
15 Refueling Cavity Leakage Fall 2009 Unit 1 Repairs Repaired Embedment Plate Configuration Existing 1/4" thk stainless steel cavity liner New seal weld between baseplate and embedment plate Existing cavity liner fillet weld to embedment plate Side View Replace existing nuts with fabricated blind nuts seal welded to baseplate
16 Refueling Cavity Leakage Fall 2009 Unit 1 Repairs
17 Refueling Cavity Leakage Fall 2009 Unit 1 Repair Results z Repair of Floor Embedment Plates Eliminated that Leakage Source z ECCS Sump z No Evidence of Leakage z Minor Leakage Observed on Ceiling of Regenerative Heat Exchanger Room z Appeared After Cavity Flooded 14 Days z Estimated to be 0.05 Gallons per Hour Containment Elevation
18 Refueling Cavity Leakage Fall 2009 Unit 1 Repair Results z No Evidence Leakage Reached Containment Vessel z No Leakage Through Wall in ECCS Sump z No Leakage at Intersection of Transfer Tube and Containment Vessel Concrete z Minor Leakage Observed in Regenerative Heat Exchanger Room Containment Elevation
19 Refueling Cavity Leakage Fall 2009 Unit 1 Testing and Inspection z Original Scope of Testing and Inspection z Vacuum Box Testing of Refueling Cavity Liner Plate Seam Welds - No Leakage Identified z NDE of Fuel Transfer Tube Welds - No Indications z Expanded Inspections in Response to Remaining Leakage z NDE of Liner to Floor Embedment Plate Fillet Welds z One Porosity Indication z Will be Repaired During Next Unit 1 Refueling Outage
20 Refueling Cavity Leakage Evaluation of Remaining Unit 1 Leakage z Evaluation of Source of Remaining Unit 1 Leakage z RCCA Guide Box Wall Embedment Plates z Design Similar to Floor Embedment Plates z Will be Repaired During Next Unit 1 and 2 Refueling Outages z Evaluation of Other Potential Leakage Sources z Will Identify any Additional Inspections and Repairs Prior to Next Unit 1 and Unit 2 Refueling Outages
21 Refueling Cavity Leakage 2010 Unit 2 Corrective Actions z Repair of Reactor Vessel Internals Stands and RCCA Change Fixture Floor Embedment Plates z Repair of RCCA Guide Box Wall Embedment Plates z NDE of Fuel Transfer Tube Welds z Vacuum Box Testing of Refueling Cavity Liner Plate Seam Welds z NDE of Liner to Floor Embedment Plate Fillet Welds z Other Inspections and Repairs Resulting From Evaluation of 2009 Unit 1 Leakage
22 Refueling Cavity Leakage 2011 Unit 1 Corrective Actions z Repair of RCCA Guide Box Wall Embedment Plates z Repair of Liner to Floor Embedment Plate Fillet Weld Porosity Indication z Other Inspections and Repairs Resulting From Evaluation of 2009 Unit 1 and 2010 Unit 2 Repair Results
23 Refueling Cavity Leakage Monitoring and Assessment z Ultrasonic and Visual Examinations of Containment Vessel Through ECCS Sump Wall z Unit 1 and 2 (Prior to 2009) z Grout Removed z Wall Thickness at or Above ASTM Specifications z No Corrosion of Containment Vessel z Unit 1 (Fall 2009) z Grout Removed z Wall Thickness at or Above ASTM Specifications z No Corrosion of Rebar or Containment Vessel Sump Section Containment Elevation
24 Refueling Cavity Leakage Monitoring and Assessment Unit 1 ECCS Sump Fall 2009 z Grout not Degraded z Ribs on Rebar Intact z Containment Vessel z No Wet Areas or Leakage
25 Refueling Cavity Leakage Monitoring and Assessment z Ultrasonic Examination of the Containment Vessel from the Annulus z Unit 2 (2008) and Unit 1 (2009) z Examined Areas:
z From Transfer Tube Toward ECCS Sump z Above and Behind ECCS Sump z Wall Thickness at or Above ASTM Specifications Annulu s Photo
26 Refueling Cavity Leakage Monitoring and Assessment - Commitments z Commitments for Next Refueling Outage in Each Unit Following Embedment Plate Repairs z
Removal of Concrete from Sump Below Reactor Vessel to Expose Containment Vessel z
Inspect (VT and UT) Containment Vessel z
Assessment of Exposed Concrete z
Petrographic Examination of Removed Concrete z
Removal of Concrete Sample Wetted by Borated Water Leakage from Refueling Cavity z
Concrete will be Tested For Compression Strength and will Undergo Petrographic Examination Containment Elevation
27 Refueling Cavity Leakage Monitoring and Assessment - Commitments z Commitment for Next Two Consecutive Refueling Outages in Each Unit Following Embedment Plate Repairs z Monitor Areas Previously Exhibiting Leakage to Confirm That Leakage has not Recurred
28 Refueling Cavity Leakage Long Term Aging Management z Continue to Manage Aging of the Containment Structures and Vessel Using the Structures Monitoring Program and ASME Section XI, Subsection IWE Program z Utilize Corrective Action Program for Evaluation and Correction of New Issues
29 Refueling Cavity Leakage Evaluation of Potential Degradation z The Potential for Degradation of the Steel Containment Vessel and Reinforced Concrete (Concrete/Rebar) was Evaluated z Evaluation Concluded:
z Any Potential Corrosion of the Containment Vessel Behind Concrete in Areas Wetted by Refueling Cavity Water Would be Minor z No Significant Effect on Reinforced Concrete That Has Been Wetted by Refueling Cavity Water
30 Refueling Cavity Leakage z In Summary, z No Degradation Found to Date z Evaluation of Potential Degradation Indicates Low Safety Significance z Committed to Eliminate Refueling Cavity Leakage
31 ACRS LR Subcommittee Follow-Up Items Condensate Storage Tank Examinations
32 Condensate Storage Tank Examinations z Aboveground Steel Tanks Program Included UT Inspection of the Bottom of 1 of the 3 Condensate Storage Tanks Prior to PEO z ACRS LR Subcommittee Questioned Whether an Inspection of Only 1 Tank Would Assure Acceptability of all 3 Tanks z LRA Change Submitted on August 7, 2009 Which Revised the Aboveground Steel Tanks Program to Include UT Inspection of the Bottom of all 3 Condensate Storage Tanks Prior to PEO
33 ACRS LR Subcommittee Follow-Up Items Underground Medium Voltage Cables Manhole Inspection Interval Impact of Freeze/Thaw Conditions
34 Underground Medium Voltage Cables Manhole Inspection Interval z ACRS LR Subcommittee Questioned Adequacy of Two Year Manhole Inspection Frequency z Inspection Frequency is Based on Actual Plant Experience, but not to Exceed Every Two Years z Consistent with GALL XI.E3 z One Manhole in Scope of License Renewal z Five Inspections Since September 2007 Have Shown no Signs of Water Intrusion or Accumulation
35 Underground Medium Voltage Cables Manhole Inspection Interval z Design Precludes Water Accumulation z Floor of Gravel and Sand z Approximately Ten Feet Above Water Table z Grade Around Manhole Precludes Significant Rain Water Intrusion z Based on Manhole Design and Actual Plant Experience, Two Year Inspection Frequency is Considered Sufficient
36 Underground Medium Voltage Cables Manhole Inspection Interval
37 Underground Medium Voltage Cables Impact of Freeze/Thaw Conditions z Prairie Island Operating Experience was Reviewed for Evidence of Accelerated Cable Insulation Aging Related to Freeze/Thaw Conditions z The Following Organizations were also Contacted:
z Monticello Nuclear Generating Plant z Xcel Energy Distribution z EPRI z NEI License Renewal Electrical Working Group z Accelerated Cable Insulation Aging Related to Freeze/Thaw Conditions has not Been Identified as an Issue
38 Questions?
39 Supporting Slides
40
41 Origin ECCS Sump Sump C Fuel Transfer Tube Regen HX Room Leak Paths ECCS Sump